r"""
Miscellaneous helper functions
"""
def _to_space_separated_string(l):
"""
Converts a container to a space-separated string.
INPUT:
- ``l`` -- anything iterable.
OUTPUT:
String.
EXAMPLES::
sage: import sage.geometry.polyhedron.misc as P
sage: P._to_space_separated_string([2,3])
'2 3'
"""
s = '';
for x in l:
if len(s)>0: s += ' '
s += repr(x)
return s
def _set_to_None_if_empty(x):
"""
Helper function to clean up arguments: Returns None if x==None or
x is an empty container.
EXAMPLES::
sage: import sage.geometry.polyhedron.misc as P
sage: None == P._set_to_None_if_empty([])
True
sage: P._set_to_None_if_empty([1])
[1]
"""
if x is None: return x
if len(x)==0: return None
return x
def _set_to_empty_if_None(x):
"""
Helper function to clean up arguments: Returns the empty list if
x==None or x is an empty container.
EXAMPLES::
sage: import sage.geometry.polyhedron.misc as P
sage: [] == P._set_to_empty_if_None(tuple())
True
sage: [] == P._set_to_empty_if_None(None)
True
sage: P._set_to_empty_if_None([1])
[1]
"""
if x is None: return []
if len(x)==0: return []
return x
def _common_length_of(l1, l2=None, l3=None):
"""
The arguments are containers or ``None``. The function applies
``len()`` to each element, and returns the common length. If the
length differs, ``ValueError`` is raised. Used to check arguments.
OUTPUT:
A tuple (number of entries, common length of the entries)
EXAMPLES::
sage: import sage.geometry.polyhedron.misc as P
sage: P._common_length_of([[1,2,3],[1,3,34]])
(2, 3)
"""
args = [];
if l1 is not None: args.append(l1)
if l2 is not None: args.append(l2)
if l3 is not None: args.append(l3)
length = None
num = 0
for l in args:
for i in l:
num += 1
length_i = len(i)
if length is not None and length_i != length:
raise ValueError, "Argument lengths differ!"
length = length_i
return num, length
